Mutant X was a comic book published by Marvel Comics featuring Havok, a mutant and former member of the X-Men, who was transported into a parallel dimension. It was written by Howard Mackie.

The "Mutant X" universe (Earth-1298) is a reimagination of the Earth-616 universe. In this continuum, Scott Summers was captured along with his parents by the Shi'ar and only Alex escaped, allowing him to be the eventual leader of the X-Men. The Mutant X universe reimagines Mister Fantastic, Nick Fury, and Professor X as villains and Doctor Doom and Apocalypse as heroes.

After a member of Havok's X-Factor team, Greystone, develops temporal insanity, he attempts to build a time machine to return to his timeline and be reunited with his mother who, in all probability, does not exist anymore. Havok attempts to stop him, but the machine explodes, supposedly killing both men. However, death was only the beginning for Alex Summers. At the instant of his death, another Havok from an alternate reality also dies after being shot in the chest by a Sentinel. Somehow, Havok's spirit finds its way into his counterpart's body and he wakes up in the Mutant X Universe. Here, he is the leader of a mutant team of heroes dubbed The Six, who are altered versions of his friends from Earth-616.

At first he finds this universe strange, thinking it to be nothing more than the mental manipulations of some megalomaniac, but in time he comes to cherish the relationships he had. The team endures many hardships together, including betrayal by the demon-possessed Madelyne and Fallen, but they compensate with the arrival of new members Gambit and Captain America.

At the end of the series, the reincarnated Goblyn Force, Dracula and the Beyonder all converge their efforts to destroy Earth. Almost all of the heroes die in the epic battle until Havok, discovering that he was the home for the Nexus of Realities, a force of nature that binds all realities (Omniverse) in which it gave Havok Omniversal level of power in which, Goblin Entity planned on using to destroy and reshape the Omniverse at her image, he then finds a way to stop the Goblin Entity, which at that time had merged with the Beyonder. He then fights with the possessed Maydelyne and harnesses the power of the Nexus of All realities and with a thought eliminates the Goblin Entity throughout the Omniverse, instantaneously. He then teleports Maydelyne to her alternate universe with her son, Scotty. Fearing that somebody would attempt to use the power of the Nexus of All Realities to reshape, destroy, or alter the very Omniverse; he then becomes one with the Nexus of All Realities to prevent anyone from getting this power, except himself.

The series lasted for 32 issues and three annuals before it ended and Alex Summers' consciousness was returned to his proper body.